Dynamic Contour Tonometry Measurements Research Articles

Correlation of Intraocular Pressure Measured With Goldmann and Dynamic Contour Tonometry in Normal and Glaucomatous Eyes

To compare intraocular pressure (IOP) values measured by both Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) in both normal and glaucomatous eyes, and to determine the relationship between these parameters and central corneal thickness (CCT). Forty-seven subjects with primary open-angle glaucoma and 38 normal subjects attended a 12-hour session during which IOP was assessed at 7 time points, every 2 hours, by both GAT and DCT. CCT was also assessed at the same visit. Mean IOP was calculated for each eye of each subject by each method from the 7 diurnal IOP measurements obtained. Mean IOP was higher when measured by DCT than by GAT in both normal (by 1.1 mm Hg, P<0.0001) and glaucomatous (by 1.6 mm Hg, P<0.0001) eyes. IOP measurements by GAT and DCT were moderately correlated in both normal (r(2)=0.354, P<0.0001) and glaucomatous (r(2)=0.552, P<0.0001) eyes. In normal eyes, there was a weak positive correlation between GAT IOP and CCT (r(2)=0.088, slope=0.022 mm Hg/microm, P=0.009) and no correlation between DCT IOP and CCT (r(2)=0.007, slope=0.005 mm Hg/microm, P=0.468). In glaucomatous eyes, there was no correlation between GAT IOP and CCT (r(2)=0.006, slope=0.007 mm Hg/microm, P=0.473) and a weak inverse correlation between DCT IOP and CCT (r(2)=0.075, slope=-0.021 mm Hg/microm, P=0.008). Both GAT and DCT are affected by CCT, albeit in different ways. Normal and glaucomatous eyes exhibit different relationships between CCT and IOP measured by either GAT or DCT. The relationships between CCT and transcorneal IOP measurements are complex and incompletely characterized, which limits the clinical interpretation of GAT and DCT measurements of IOP in both normal and glaucomatous eyes.

Effect of corneal thickness on intraocular pressure measurements with the Pascal dynamic contour, Canon TX‐10 non‐contact and Goldmann applanation tonometers in healthy subjects

Purpose: To investigate the effects of central corneal thickness (CCT) on intraocular pressure (IOP) measurements of the Pascal dynamic contour tonometry (DCT), Canon TX‐10 non‐contact tonometry (NCT) and Goldmann applanation tonometry measurements (GAT) in healthy subjects.Methods: IOP values of 135 eyes with normal corneas of 135 healthy volunteers were determined by DCT, NCT and by GAT. The CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made.Results: When DCT measurements were compared (IOP = 17.52 ± 2.0-mmHg) with NCT measurements (IOP = 16.54 ± 2.77-mmHg) and GAT measurements (IOP = 15.07 ± 2.35-mmHg), DCT measurements were significantly higher than NCT and GAT (p < 0.001). There was a significant correlation between CCT with both NCT (r = 0.260, p = 0.003) and GAT measurements (r = 0.257, p = 0.005). There was a weak correlation that was not statistically significant between CCT and DCT (r = 0.160, p = 0.079).Conclusion: The IOP measurements with DCT seem to be less dependent on CCT. NCT appears to be more affected by variation in CCT than GAT.

Estudo comparativo entre o tonômetro de aplanação de Goldmann e o tonômetro de contorno dinâmico de Pascal no glaucoma primário de ângulo aberto e olhos normais

PURPOSE: To compare intraocular pressure (IOP) readings of Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT), and to correlate central corneal thickness (CCT) with these readings. METHODS: This transversal study included patients in two groups: open-angle glaucoma (OAG) and normal eyes (NE). IOP measurements were obtained in all patients using GAT and DCT. The same examiner made all GAT measurements. Another examiner, who was masked to the GAT readings, made DCT measurements. CCT was determined by ultrasound pachimetry. RESULTS: [...]

Influence of age, central corneal thickness, and quality score on dynamic contour tonometry

To compare the IOP measurements obtained with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT), and to analyse the influence of central corneal thickness (CCT) and age on both measurements, and the influence of the quality score on DCT readings. A total of 500 healthy subjects with no prior history of glaucoma or ocular hypertension (age: 7-86 years) were consecutively recruited. GAT, DCT, and CCT measurements were obtained from both eyes of each individual, in this order, by three observers. The mean of five CCT measurements was used for analysis. DCT measurements were accepted when quality scores varied between 1 (higher quality) and 3 (lower quality). Mean DCT measurements were 3.2 mmHg higher than GAT readings. CCT values varied between 449 and 653 microm. IOP measured by GAT correlated strongly with CCT (r(2)=0.28, P=<0.001), whereas DCT readings correlated poorly with CCT (r(2)=0.01, P=0.017). Both DCT (r(2)=<0.01, P=0.044) and GAT (r(2)=0.01, P=<0.001) measurements correlated poorly with age. Bland-Altmann analysis revealed disagreement between DCT and GAT readings, with 95% confidence intervals of +/-6.7 mmHg. Quality scores for DCT measurements were 1 (n=369, 36.9%), 2 (n=340, 34.0%), and 3 (n=291, 29.1%). DCT readings with quality score of 3 (18.8+/-3.4 mmHg) were significantly higher than those with quality scores of 1 (16.7+/-2.9 mmHg) and 2 (17.4+/-2.9 mmHg; P=<0.001). DCT is not influenced by CCT, unlike GAT. Both DCT and GAT measurements are not influenced by age. DCT measurements with lower quality scores are associated with higher readings.

Corneal Parameters and Difference Between Goldmann Applanation Tonometry and Dynamic Contour Tonometry in Normal Eyes

To compare the difference between 2 methods of measuring the intraocular pressure (IOP), namely, Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) and to study the relationship with the corneal parameters in patients with no glaucoma signs. One hundred and eighteen eyes of 118 healthy subjects from 20 to 77 years of age underwent IOP measurements with DCT and GAT, central corneal thickness, and corneal volume measurements with Pentacam Scheimpflug camera. Pentacam examination has been performed first, then DCT and, after 10 minutes, GAT measurements. The measurements with GAT ranged between 11 and 22 mm Hg (m=15.49+/-2.43 mm Hg), the measurements with DCT ranged between 10.5 and 25.1 mm Hg (m=17.59+/-2.9 mm Hg). DCT showed a statistically significant (P<0.0001) higher IOP measurement compared with GAT. A relation between differences in IOP with central corneal thickness and corneal volume was found, whereas no relation was found with corneal radius and age. Our results show a discrete correlation between GAT and DCT measurements, but DCT showed slightly higher values of IOP. If DCT should be considered the gold standard, higher values of IOP could still be considered normal. These 2 devices cannot to be used interchangeably.

Ocular Pulse Amplitude in Normal Tension and Primary Open Angle Glaucoma

(1) To investigate the relationship of ocular pulse amplitude (OPA) with intraocular pressure (IOP) and corneal thickness. (2) To evaluate OPA in patients with primary open angle and normal tension glaucoma (NTG). Patients with NTG (n=28), primary open angle glaucoma (POAG) (n=19), and age-matched healthy controls (n=22) underwent 2 consecutive Goldmann and dynamic contour tonometry measurements within 1 month. Central corneal thickness was also measured. A regression model was applied to compare OPA between the diagnostic groups. OPA increased with rising IOP (slope 0.026/0.033 and P=0.002/<0.0001 for Goldmann/Dynamic tonometry), whereas corneal thickness did not influence pulse amplitude measurements (slope-0.0017/-0.0013 and P=0.11/0.21 after correction for Goldmann/Dynamic tonometry). In a multivariate model correcting for IOP and corneal thickness, OPA was reduced in patients with NTG (P=0.014/0.017 corrected for Goldmann/Dynamic tonometry) or POAG (P=0.015/0.014). OPA is reduced in normal tension and POAG patients compared with healthy controls. OPA is influenced by IOP, but not by corneal thickness.

Comparison of Goldmann applanation tonometry and dynamic contour tonometry in healthy and glaucomatous eyes

To compare the measurements of intraocular pressure (IOP) with dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in healthy and glaucomatous eyes and to evaluate the influence of corneal thickness (CCT), corneal curvature (CC), axial length (AL), and age on these tonometric alternatives. Three hundred eyes of 100 healthy subjects, 100 patients with primary open angle glaucoma, and 100 patients with primary angle-closure glaucoma underwent IOP evaluation with DCT and GAT, and measurements of CCT, CC, and AL. Bland-Altman plots were used to evaluate the agreement between tonometers. Regression analysis was used to evaluate the influence of ocular structural factors on IOP measurements obtained with both tonometers. Bland-Altman plots indicated that the 95% limits of agreement between tonometers were -1.4 to 6.6 mmHg. DCT values measured 2.6+/-1.9 mmHg higher than GAT readings (P<0.001). The mean IOP difference between DCT and GAT (DeltaIOP) was higher in healthy than in glaucomatous eyes and the magnitude of difference increased with increasing CCT. A significant reduction of DeltaIOP with an increase in both CCT (P<0.001) and IOP values (P<0.001) was found. Regression analysis showed no effect of CC, AL, and age on both DCT and GAT readings. In contrast to GAT (P<0.001), DCT measurements were not influenced by CCT (P=0.43). IOP readings obtained by DCT were higher and less affected by CCT than those by GAT. The DeltaIOP was higher in healthy than in glaucomatous eyes and decreased in relation to increased CCT and IOP values.

Clinical Comparison of Pascal Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Asymmetric Open-angle Glaucoma

To investigate and compare the relationships between glaucomatous visual field loss and intraocular pressure (IOP) as measured by both Pascal dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT). All primary open-angle glaucoma and normal tension glaucoma patients seen between July 2005 and June 2006 with at least 2 sets of good-quality, bilateral DCT and GAT measurements were retrospectively identified. Additional inclusion criteria required that all subjects had repeatable, asymmetric glaucomatous visual field loss that corresponded with asymmetric glaucomatous optic neuropathy. After mean IOP values were computed and visual fields were scored using Advanced Glaucoma Intervention Study (AGIS) criteria, paired-eye comparisons were conducted using right versus left eyes and higher versus lower AGIS-score eyes. Sixty-seven (42 primary open-angle glaucoma, 25 normal tension glaucoma) subjects met all criteria for study inclusion. Per paired t test, mean DCT-IOP was significantly higher in the higher AGIS-score eyes compared with the lower AGIS-score eyes (16.3 vs. 15.5 mm Hg, P=0.004), whereas GAT-IOP was not significantly different in these same eyes (14.5 vs. 14.4 mm Hg, P=0.56). Mean IOP difference between the 2 methods was significantly larger in higher versus lower AGIS-score eyes (P<0.001), and 72% of the subjects demonstrated larger intermethod IOP differences in their higher AGIS-score eye compared with their lower AGIS-score eye (P<0.001; 95% confidence interval: 0.59-0.82). Multivariate linear regression analysis revealed that AGIS-score differences between eyes were independently associated with both intermethod IOP differences between eyes (P=0.004) and central corneal thickness (CCT) differences between eyes (P=0.04). CCT, however, was not associated with intermethod IOP differences within or between eyes. These findings suggest that DCT-IOP is correlated with glaucomatous damage, and moreover, DCT-IOP is more closely related to extent of glaucoma damage than is GAT-IOP. The most likely explanation for these results is that GAT-IOP systematically underestimates IOP compared with DCT-IOP. Our findings also support the hypothesis that corneal biomechanical factors other than CCT are major confounders of applanation tonometry measurements.

Effect of Central Corneal Thickness on Dynamic Contour Tonometry and Goldmann Applanation Tonometry in Primary Open-angle Glaucoma

To compare the dependence of dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) on central corneal thickness (CCT) in primary open-angle glaucoma. In a prospective study, the interocular (right vs left eye) difference in intraocular pressure measured by DCT and GAT was compared with the interocular CCT difference in 125 patients with primary open-angle glaucoma. Dynamic contour tonometry measurements (mean +/- SD, 19.4 +/- 4.1 mm Hg) were significantly (P=.004) higher than GAT measurements (mean +/- SD, 15.5 +/- 3.4 mm Hg), correlating significantly with each other (r(2)=0.82, P<.001). The interocular difference in intraocular pressure correlated significantly with the interocular CCT difference for GAT (r=0.30, P=.001) and DCT (r=0.23, P=.02) readings. Dynamic contour tonometry and GAT intraocular pressure differences significantly increased with older age (slope, 0.033 [95% confidence interval, 0.002-0.064] mm Hg/y; P=.03) but not with thicker CCT (slope, 0.006 [95% confidence interval, -0.003 to 0.017] mm Hg/mum; P=.22). In this series, GAT and DCT measurements were dependent on CCT in patients with primary open-angle glaucoma. Because intraocular pressure differences between DCT and GAT were independent of CCT, DCT and GAT are susceptible to similar measurement biases depending on CCT.

Comparison of Dynamic Contour Tonometry and Goldmann Applanation Tonometry in African American Subjects

To evaluate the relationship between intraocular pressure (IOP) measurements obtained by dynamic contour tonometry (DCT) and Goldmann applanation tonometry (GAT) in African Americans and to assess whether these measures were influenced by ocular parameters including corneal thickness, corneal curvature, and axial length. Observational clinical study. The study included 176 eyes of 94 African Americans. All participants underwent IOP evaluation with DCT and GAT, as well as measurements of central corneal thickness (CCT), corneal curvature, corneal astigmatism, spherical equivalent, and axial length. Univariate and multiple regression analyses were used to evaluate the associations between IOP (as measured with DCT and GAT) and CCT, corneal curvature, corneal astigmatism, spherical equivalent, axial length, and age. Bland-Altman plots were used to evaluate the agreement between IOP measurements obtained by DCT and GAT. In multiple regression analysis, GAT IOP measurements were significantly associated with CCT (P<0.001) and age (P = 0.003), whereas DCT IOP measurements were associated only with age (P = 0.027). The difference between DCT and GAT IOP measurements was significantly influenced by corneal thickness (P<0.001) and ocular pulse amplitude (OPA; P = 0.004). Patients with thick corneas tended to have higher GAT IOP measurements compared with DCT, whereas in patients with thin corneas, GAT IOP measurements tended to be lower than DCT measurements. Larger values of OPA were associated with a decrease in the difference between DCT and GAT measurements, whereas smaller values of OPA were associated with an increase in the difference between DCT and GAT measurements. Dynamic contour tonometry measurements in African Americans seem to provide an estimate of IOP that is less influenced by corneal properties than those provided by GAT.

Comparisons between Pascal dynamic contour tonometry, the TonoPen, and Goldmann applanation tonometry in patients with glaucoma

To compare intraocular pressure (IOP) measurements taken with Pascal dynamic contour tonometry (DCT), the TonoPen and the Goldmann applanation tonometry (GAT). The influence of central corneal thickness (CCT) on IOP measurements taken with Pascal DCT and the TonoPen was evaluated. One eye in each of 101 consecutive patients with primary open-angle glaucoma (POAG) underwent ultrasonic CCT measurement and IOP evaluation with GAT, Pascal DCT and the TonoPen in random order. The agreement between results from Pascal DCT and the TonoPen and those of GAT was assessed using the Bland-Altman method. The deviation of Pascal DCT and TonoPen readings from GAT values, corrected for CCT, was calculated and correlated to CCT using a linear regression model. The mean of the differences in IOP measurements was 3.2 +/- 2.4 mmHg for Pascal DCT minus GAT readings and 0.5 +/- 4.5 mmHg for TonoPen minus GAT readings. The 95% confidence interval of differences in IOP measurements was higher between TonoPen and GAT readings (- 6 to 7 mmHg) than between Pascal and GAT readings (0.1-6.8 mmHg). Pascal DCT significantly overestimated IOP compared with GAT, especially for higher IOP readings. Bland-Altman scatterplots showed reasonable inter-method agreement between Pascal DCT and GAT measurements, and poor agreement between TonoPen and GAT measurements. The deviations of Pascal DCT and TonoPen readings from the corrected GAT values were both highly correlated with CCT values (linear regression analysis, p < 0.0001). The mean change in measured IOP for a 10-microm increase in CCT was 0.48 mmHg for Pascal DCT and 0.74 mmHg for the TonoPen. Agreement with GAT measurements was higher for Pascal DCT than for TonoPen readings; however, Pascal DCT significantly overestimated IOP values compared with GAT. Measurements of IOP obtained with both Pascal DCT and the TonoPen appeared to be influenced by CCT, and this influence appeared to be greater for the latter.

Dynamic Contour Tonometry

To compare intraocular pressure (IOP) measurements in patients with keratoconus (KC), pellucid marginal degeneration (PMD), and unilateral penetrating keratoplasty (PK) for KC by Goldmann applanation tonometry (GAT), Tono-Pen tonometry (TP), and Pascal dynamic contour tonometry (DCT). Patients with KC, PMD, or PK were included in a prospective study. IOPs were measured by GAT, TP, and DCT. Severity of ectasia was determined by the steep curvature by corneal topography and central thinning by contact ultrasound pachymetry. IOP measurements were compared and correlated with disease severity. Fifty-three eyes of 36 patients were enrolled. Mean age was 45.3 +/- 12.5 years (range: 28-72 years). Twenty-nine eyes had KC, 21 eyes had a PK for KC, and 3 eyes had PMD. Mean DCT, GAT, and TP readings were 16.1 +/- 2.9, 14.3 +/- 4.1, and 13.8 +/- 4.1 mm Hg, respectively. The differences of mean IOP between GAT and DCT and TP and DCT were statistically significant, whereas the difference between GAT and TP was not. Both GAT and TP readings were significantly higher in the PK eyes than the KC and PMD eyes, whereas DCT readings were not. DCT measurements were not significantly different in PK versus non-PK eyes. DCT is a newly Food and Drug Administration (FDA)-approved device that is designed to measure IOP, independent of corneal thickness, corneal curvature, and ocular rigidity. DCT gave significantly higher IOP readings than GAT and TP in this study. DCT readings were not affected by corneal thickness. DCT may be more accurate in IOP measurement in eyes with KC and PMD.

Measurement of intraocular pressure after LASIK by dynamic contour tonometry

Changes of corneal properties induced by laser in situ keratomileusis (LASIK) results in low inaccurate intraocular pressure (IOP) readings by Goldmann applanation tonometry (GAT). Before and after LASIK, the applied value of IOP, measured by dynamic contour tonometry (DCT) in comparison to GAT, was evaluated. Before and 1, 4 weeks after LASIK, the IOP in 30 cases (60 eyes) was measured by GAT and DCT respectively. The obtained results were statistically processed by SPSS11.5 statistical software. The results showed that central corneal thickness (CCT) could affect GAT measurements but not DCT measurements. The comparison of IOP one and 4 weeks after LASIK revealed that the readings from GAT was separately decreased by 5.00 +/- 1.12 and 5.45 +/- 1.13 mmHg as compared with those before LASIK, while those from DCT had no significant difference. It was concluded that LASIK-induced changes of CCT could influence the accuracy of GAT measurements, but had no influence on those from DCT. DCT was more beneficial to the measurements of IOP in normal eyes and those subject to LASIK surgery.

Intraocular Pressure and Ocular Pulse Amplitude Comparisons in Different Types of Glaucoma Using Dynamic Contour Tonometry

Purpose: To compare the intraocular pressures (IOP) and ocular pulse amplitudes (OPA) in patients with different types of glaucoma, ocular hypertension (OHT), and normal controls (NC) using dynamic contour tonometry (DCT) and the goldmann applanation tonometry (GAT). Methods: 906 eyes of 501 adult patients in the following five groups were included in this cross-sectional study: primary open angle glaucoma (POAG), normal tension glaucoma (NTG), Pseudoexfoliative Glaucoma (PXG), OHT, and NC. The following tests were performed simultaneously during a single visit: IOP using DCT and GAT; OPA using DCT and central corneal thickness (CCT) using ultrasound pachymetry. Mixed effects regression models were used to compare the DCT and GAT IOP measurements in the five groups; the effect of CCT on IOP and the relationship between OPA and IOP within each group. Results: DCT consistently had higher IOP values than GAT in POAG, PXG, NTG, and controls (p < 0.001) but not in OHT (p = 0.84). DCT IOP did not change while GAT IOP showed a non-significant increase (p = 0.09) with increased corneal thickness in each group. OPA was found to be highest in OHT (3.61 mmHg) and lowest in the control group (2.86 mmHg) and significantly increased with IOP in all groups. Conclusions: DCT measures an IOP that is significantly higher than GAT IOP in glaucoma and control subjects but not in ocular hypertensives. Furthermore, the DCT may measure an IOP that is independent of the CCT, which may not be true for the GAT, which increases with the CCT. OPA was highest in OHT and may be affected by the IOP.